Who is Giller from Wizard's First Rule and what is their importance?

Giller is Zedd's second-in-command and most trusted wizard ally until, like the other wizards, he sells out by becoming involved in politics. Giller is assigned the important job of guarding Kahlan, the Mother Confessor but he decides to go to work for the evil Queen Milena instead. Eventually Giller realizes that the Queen is victimizing innocent villagers. He feels great guilt over the abuse of innocent people, including Rachel's poor treatment by Princess Violet.